For example, in Patent Document 1 shown below, there is disclosed a seat back frame for a vehicle seat in which a supporting plate is provided. The supporting plate rapidly reduces the clearance between the head of an occupant and the headrest when receiving an impact load from a vehicle rear part, so that the upper part of the pelvis of the occupant seated on the seat is supported from the back surface side.
In the case of the seat back frame, the front surface side of the supporting plate is formed flat, and the left and right end portions of the supporting plate are coupled to a side frame of a frame main body. Therefore, when receiving an impact from the rear of the vehicle, the waist of the occupant is first supported by the supporting plate. This allows the chest and head of the occupant to tilt backward at the waist (the upper pelvis). As a result, the head approaches the headrest quickly.
In addition, for example, in Patent Document 2 shown below, there is disclosed a seat back frame for a vehicle seat in which a back plate that is a plate-shaped reinforcement member is coupled to a rear part of the left and right side frames, so that when receiving an impact load from a vehicle side part, the load is transmitted from the side frame on the outer side in the vehicle width direction to the side frame on an inner side through the back plate.
In addition, for example, in Patent Document 3 shown below, there is disclosed a seat back frame for a vehicle seat in which a reinforcement pipe that is extended to the outer side in the vehicle width direction exceeding the width of a seat back is provided in a rear part of the left and right side frames, so that an impact load input from the side of the vehicle is transmitted to a central side of a vehicle body through the reinforcement pipe.
However, as for this seat back frame, the reinforcement pipe which has a large outer diameter is disposed in the rear part of the side frame, so that the front and rear widths of the seat back are increased to cause an increase in the size of the seat.
Meanwhile, for example, in Patent Document 2 shown below, there is disclosed a seat back frame in which a load transmission member protruded to the outer side in the vehicle width direction is provided to the side frame on the outer side in the vehicle width direction, so that back surfaces of the left and right side frames are coupled to each other by a reinforcement plate.
In the seat back frame, when the impact load is input from the side of the vehicle body, the load is transmitted from the load transmission member to the side frame on the outer side in the vehicle width direction. In addition, the load is transmitted from the side frame to another side frame on the inner side in the vehicle width direction through a rear side reinforcement plate.